The CDC and the World Health Organization have said the risk of travelers contracting the disease was remote, since Ebola doesn’t spread easily through casual contact, and is not airborne or food borne.

But with the West African health system deep in the throes of the outbreak, the CDC is concerned that travelers with medical emergencies unrelated to Ebola – a broken leg or a heart attack – might be exposed to the disease at a hospital.

“What has concerned us is the possibility that healthcare facilities in the region … might be deeply stressed because of the Ebola challenge, and second, there might be a risk that you were exposed to Ebola,” said CDC Director Tom Frieden.

Frieden said the United States is sending a “surge” of about 50 CDC personnel to West Africa, in an effort to “begin to turn the tide” against the disease.

If a traveler from West Africa does enter the U.S. after becoming ill, Frieden said, the CDC is confident that American health systems have the capacity to contain Ebola’s spread.